Wireless mobile communication technology uses various standards and protocols to transmit data between a node (e.g., a transmission station or a transceiver node) and a wireless device (e.g., a mobile device). Some wireless devices communicate using orthogonal frequency-division multiple access (OFDMA) in a downlink (DL) transmission and single carrier frequency division multiple access (SC-FDMA) in an uplink (UL) transmission. Standards and protocols that use orthogonal frequency-division multiplexing (OFDM) for signal transmission include the third generation partnership project (3GPP) long term evolution (LTE) Rel. 8, 9 and 10, the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard (e.g., 802.16e, 802.16m), which is commonly known to industry groups as WiMAX (Worldwide interoperability for Microwave Access), and the IEEE 802.11-2012 standard, which is commonly known to industry groups as WiFi.
In a 3GPP radio access network (RAN) LTE system, the node can be a combination of Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node Bs (also commonly denoted as evolved Node Bs, enhanced Node Bs, eNodeBs, or eNBs) and Radio Network Controllers (RNCs), which communicate with the wireless device, known as a user equipment (UE). The downlink (DL) transmission can be a communication from the node (e.g., eNodeB) to the wireless device (e.g., UE), and the uplink (UL) transmission can be a communication from the wireless device to the node.
In homogeneous networks, the node, also called a macro node, can provide basic wireless coverage to wireless devices in a cell. The cell can be the area in which the wireless devices are operable to communicate with the macro node. Heterogeneous networks (HetNets) can be used to handle the increased traffic loads on the macro nodes due to increased usage and functionality of wireless devices. HetNets can include a layer of planned high power macro nodes (or macro-eNBs) overlaid with layers of lower power nodes (small-eNBs, micro-eNBs, pico-eNBs, femto-eNBs, or home eNBs [HeNBs]) that can be deployed in a less well planned or even entirely uncoordinated manner within the coverage area (cell) of a macro node. The lower power nodes (LPNs) can generally be referred to as “low power nodes”, small nodes, or small cells.
The macro node can be used for basic coverage. The low power nodes can be used to fill coverage holes within a macro node's geographic coverage area (i.e. cell) and at the boundaries between the macro nodes' coverage areas. Low power nodes can also be used to improve capacity in high use areas and improve indoor coverage where building structures impede signal transmission.
Homogeneous networks or HetNets can use time-division duplexing (TDD) or frequency-division duplexing (FDD) for DL or UL transmissions. Time-division duplexing (TDD) is an application of time-division multiplexing (TDM) to separate downlink and uplink signals. In TDD, downlink signals and uplink signals may be carried on a same carrier frequency where the downlink signals use a different time interval from the uplink signals, so the downlink signals and the uplink signals do not generate interference for each other. TDM is a type of digital multiplexing in which two or more bit streams or signals, such as a downlink or uplink, are transferred apparently simultaneously as sub-channels in one communication channel, but are physically transmitted on different resources. In frequency-division duplexing (FDD), an uplink transmission and a downlink transmission can operate using different frequency carriers. In FDD, interference can be avoided because the downlink signals use a different frequency carrier from the uplink signals.
Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.